They compare average temperatures at any given time and place to a long-term average, or base period, for each area.

在每个地区，他们都用一个时间点的平均气温和长期或者一段时间内的平均气温进行比较。

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"Whenever you work at a company for a period of time, you begin to build a power base," says Dr. Potter.

“无论何时，你在一个公司工作一段时间，你开始建立一个权力基础，”波特博士说。

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The 30 to 50 American troops stationed at Point Alpha were on call 24 hours a day for six weeks at a time and were rarely permitted to leave their base during that period.

在阿尔法哨所有30—50名美军人员，他们24小时执勤，每六周轮换一次，在此期间基本不允许离开基地。

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Back to Karkand is a massive, themed expansion pack available for a period of time after the base game, developed by a separate team at DICE who last created Battlefield: Bad Company 2 Vietnam.

FORBES: Electronic Arts' DICE Responds to Battlefield 3 DLC Controversy

Created by long-time base jumper and skydiver, Ossie Khan, and shot over a two-year period, Experience Zero Gravity reveals some of the most stunning base jumping locations in Europe.

BBC: Base jumping: The serene side we��ve never seen